Matrix and adhesive resins currently available for fabricating structural composites have certain limitations. Because of their poor thermooxidative stability and moisture sensitivity, aliphatic systems in general have limited use temperatures. While certain aromatic and aromatic-heterocyclic systems on the other hand are moisture insensitive, they are not completely satisfactory as a result of their poor processing parameters.
The primary processing problem inherent in a substantial number of aromatic-heterocyclic systems is the absence of an effective method for curing these systems. Aromatic and aromatic-heterocyclic systems are conventionally cured by interchain chemical reactions. This curing method requires high temperatures since extensive flow is mandatory. Because of their inherent rigidity, aromatic and aromatic-heterocyclic resins are much more susceptible to mobility dependence than are aliphatic resins. There is a need, therefore, for an entirely different method of cure that is not dependent upon extensive molecular mobility.
It is an object of this invention, therefore, to provide aromatic heterocyclic resins which can be cured by intramolecular reactions requiring only rotational movement of the polymer backbone.
Another object of the invention is to provide polyimides containing phenylethynyl pendant groups, which will cyclize and cure intramolecularly.
A further object of the invention is to provide a process for preparing the polyimides.
Other objects and advantages of the invention will become apparent to those skilled in the art upon consideration of the accompanying disclosure.